Often, in the treatment of various diseases, it may be desirable to treat a body organ, blood vessel or the like with medicine or drugs in a high concentration. Although desirable, the practice often may not be achievable because in order to apply the potentially toxic medicament in a sufficiently high dose to be effective in the region to be treated, the body may become flooded with dangerously high levels of the medicament which could result in damage to other parts of the body or could even be life threatening. For example, it has been found experimentally in animals that very high concentrations of heparin (or a particular component of heparin) when infused into the blood circulation tend to inhibit smooth muscle cell proliferation. See "Inhibition of Rat Arterial Smooth Muscle Cell Proliferation by Heparin" by John R. Guyton, et al., Circulation Research, Vol. 46, No. 5, May 1980, pp. 625-633; and "Vascular Smooth Muscle Proliferation Following Balloon Injury is Synergistically Inhibited by Low Molecular Weight Heparin and Hydrocortisone", John V. Gordon, et al., Circulation 76:IV-213, 1987. This may be of significance in connection with percutaneous transluminal angioplasty procedures by which an arterial stenosis is expanded to restore blood flow through an artery. Among the significant problems currently facing physicians practising angioplasty is that there is a relatively high rate of restenosis (of the order of 30%) after performing the initial angioplasty. It is believed that a significant contributing factor to restenosis may be smooth muscle cell proliferation of the artery wall. See "Intimal Proliferation of Smooth Muscle Cells as an Explanation for Recurrent Coronary Artery Stenosis After Percutaneous Transluminal Coronary Angioplasty" by Garth E. Austin, et al., Journal American College of Cardiology, Vol. 6, No. 2, August 1985, pp. 369-375. Thus, it may be advantageous to apply concentrated doses of heparin to an arterial wall that has been treated with angioplasty since effective doses of the heparin would be dangerous if introduced into the general circulation.
Although the desirability of applying high doses of medication to a local region of an artery or other body vessel has been recognized (see applicant's copending application Ser. No. 042,569 filed Apr. 21, 1987, now U.S. Pat. No. 4,824,432, and U.S. Pat. No. 4,423,725 issued Jan. 3, 1984 to Baran), there remains a need for an improved catheter for delivering such high concentrations without also flooding the patient's system with an unacceptably large concentration of the medication.
It is among the general objects of the invention to provide a method and apparatus for delivering high concentrations of medication to a localized area of a body vessel and to apply such medicine under pressure to cause penetration of the medicine into the wall of the body vessel, but without delivering large doses of the medication to the patient's overall system.